1. Field of the Invention
The invention relates to a repeatedly operable valve that may be inserted in a conduit of a subterranean well and operated to a closed position upon the withdrawal of a tubular work string or production string from the well to protect the underlying formation from fluids contained in the well above the valve.
2. Description of the Prior Art
A number of operations are performed in the completion and maintenance of subterranean wells that require the introduction of fluids into the well and the production formation for specific purposes. For example, subsequent to gravel packing, completion fluids are introduced to the well to displace the fluid used during the gravel packing procedure. When the gravel packing and completion fluid introduction operations are completed, it is, of course, necessary to remove the mandrel and associated wash tube of the gravel packing apparatus and, in particular, the tubular work string carrying such apparatus, and substantial quantities of completion fluid are normally contained in the removed apparatus. It is, therefore, desirable to prevent the loss of such costly fluid by flow into the formation upon the removal of the tubular work string and the associated gravel packing apparatus from the well.
There is, therefore, a distinct need for a valve which may be inserted into the well above a production formation which will be automatically operable to an open position through the insertion of a work string or production string down to the production formation and automatically shifted to a closed position upon the removal of the work string or production string to prevent the loss of fluids contained in the well as the work string is removed.